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Original question:

Isolation Amplifier

TIDA-00555

beesetty rajesh
Expert 1055 points
Other Parts Discussed in Thread: TIDA-00555, UCC12050, ISO224, TIDA-010065, TIDA-01540

H All,

I choosed  IDA-00555 reference circuit for measuring voltage (230V rms). The reference circuit used +5.0V_PH and - 5.0V_PH at the input of the AMC1100DUBR (Pg: 50/56).

I found some issues with this circuit.

1. - 5.0V_PH is mandatory must be used?

2. Pg: 51/56  The part number 750342271 (transformer) is not available as it seems to be TI customized product. Could you suggest alternate circuit to get +/- 6 Volt (isolated)

  • 0
    TI__Guru** 121988 points

    Hello Rajesh 

    Thank you for considering TIDA-00555. If you analyze the input, these supplies that you mentioned are used for protection.

    Please refer to the blow TI design 

    https://www.ti.com/tool/TIDA-010065

    The isolated supply is generated by an IC UCC12050 available fro TI and this should make it simple for you.

    The transformer is supported by wurth

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Expert 1055 points

    Hello Srinivasa,

    Thank you for your quick reply.

    I am looking for a TI reference circuit similar to TIDA-01006 which is using ISO224 that takes +-12 volt which sorts out magnetic interference issues. But I am expecting the o/p voltage to be 0-3 Volt so that I can give directly to C2000 microcontrollers.

    Kindly share any circuit if available.

  • 0 in reply to beesetty rajesh
    TI__Guru** 121988 points

    Hello Rajesh, 

    Good to know you are looking at TIDA-010065. Regarding the differential output of iso amp to single ended 0-3.3V conversion please look at the below reference design.

    https://www.ti.com/tool/TIDA-01540

    Please refer to page 2 or 3. The op-amp selection will depend on the cost and performance requirement. 

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Expert 1055 points

    Hello Sir,

    Thank you for your quick reply

    The reference ("TIDA-01540") you mentioned doesn't consist of AC voltage measurement and it doesn't consists of ISO224 too.

    I'm looking for a reference circuit to measure AC voltage (approx 500 Volt) which uses ISO224 and gives 0-3 Volt single ended signal output.

    I'm sticking to ISO224 as it takes +-12 Volts; so that EMI/EMC issues will be sorted out.

  • 0 in reply to beesetty rajesh
    TI__Guru** 121988 points

    Hello Rajesh,

    Thank you for the mail. ISO224 is an excellent device when you are looking at measuring up to 12V.

    The reference designs are based on applications. Please note that you will not find exactly matching circuit for your application in one design.

    You will have to use the TIDA-010065 for the measurement portion and TIDA-01540 for conversion to 3.3V and combine them into the application that you are looking to develop.

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Expert 1055 points

    Hello Sir,

    The voltage across  ISO224 in the page 27/51, is coming out to be

    V1 (AC input at J14) = 300 Volt (assuming peak 300Vp of AC voltage mentioned in page 1/51) 

    V2 = 0.402 Volts (V2 =- V1*R2 / (R1+ R2)) 

    The notations I'm using is shown in the image I attached.

    But the voltage should be 12 volts max at the input of ISO224. But I'm getting only maximum 0.402 volt only when 300Volt is applied.

    I'd like to confirm the voltage divider resistors.

  • 0 in reply to beesetty rajesh
    TI__Guru** 121988 points

    Hello Rajesh, 

    No worries, Please refer to the PDF schematics where R61 is DNP ( not populated). Please remove the 2.4K parallel resistor (R61) and you should get the expected voltage. Please remember that multiple resistors are provided to adjust the voltage.

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Expert 1055 points

    Sir,

    Even without 2.4K  (R61) the voltage is coming out to be 3.8 Volt with 300 Volts input.

    Even if it is assumed 300 volt to be rms, it would be 5.5 volt maximum !

    Please do the needful

  • 0 in reply to beesetty rajesh
    TI__Guru** 121988 points

    Hello Rajesh 

    For 300V the expected RMS value is around 3.8V and looks fine. 

    The current divider is configured to measure ~600V. If you want to use the same for 300V please increase the divider value. ( increase the 21K may be to 40K)

    Also, the isolation amplifier +/- 12V is peak and the RMS input will be ~8.5V. If you are looking at RMS values remember to multiply by 1.414 to calculate he peak values.

    Regards,

    Sreenivasa